The American Softwood Lumber Standard PS 20, of the U.S. Department of Commerce, relates lumber size to moisture content. Separate size schedules for green and dry lumber assure that both products will approximate the same size in service. All bills and invoices are required to show actual net sizes of lumber. Strength and stiffness values for Southern Pine products in current SPIB Grading Rules have been approved by the Board of Review of the American Lumber Standard Committee. PS 20 provides for a National Grading Rule (NGR) for Dimension Lumber1 with simplified grade names and sizes to assure uniformity, efficiency and economy in the use of dimension lumber. The NGR was incorporated in the SPIB Standard Grading Rules for Southern Pine Lumber, published by the Southern Pine Inspection Bureau.

Dimension lumber sizes and grades are

Structural Light Framing:

2″ to 4″ thick, 2″ to 4″ wide
Select Structural, No.1, No.2, No.3
Select Structural, No.1 and No.2 grades also include Dense and NonDense options.

Light Framing:

2″ to 4″ thick, 2″ to 4″ wide
Construction, Standard, Utility

Studs:

2″ to 4″ thick, 2″ and wider
Stud

Structural Joists & Planks:

2″ to 4″ thick, 5″ and wider
Select Structural, No.1, No.2, No.3
Select Structural, No.1 and No.2 grades also include Dense and NonDense options.

(1) NGR applies to dimension lumber and excludes items such as crossarms, factory and shop lumber, finish (selects), foundation lumber, industrial clears, ladder stock, laminating stock, railroad stock, rough lumber, scaffold planks, ship decking and plank stock, stadium plank, worked lumber, and special product rules for items such as radius edge decking, and prime & merchantable dimension.